THE ABSORPTION OF THE FOOD-STUFFS 



741 



According to Altmann the fat granules found in the cells during absorption are them- 

 selves produced by a transformation of fuchsinophile granules which are present in the 

 cell even during the fasting condition. At an early stage the small fat granules can be 

 stained so as to show a distinct fuchsinophile envelope. Altmann interprets this ap- 

 pearance as showing that the epithelial cells take up the fat in a dissolved form, probably 

 in a hydrolysed condition, and that a process of synthesis then occurs in the granules 

 leading to the formation and accumulation of fat. When the process of absorption is 

 proceeding actively the meshes of the villus contain a number of free fat granules, and 

 the leucocytes in these meshes are generally found also full of these granules. According 



FIG. 351. A. Vertical section through intestinal epithelium of a rat during 

 fat absorption. B. Horizontal section through deeper parts of the cells, 

 showing excretion of fine fat globules into the intercellular clefts. (RETJTER.) 



to Zawarykin and Schafer an important function in the transfer of the granules from 

 epithelial cells to central lacteal was performed by the leucocytes. These were supposed to 

 take up the fat granules extruded by the epithelial cells at the base of the villi, to wander 

 into the central lacteal where they broke down, furnishing in this way the molecular 

 basis of the chyle as well as its protein constituents. This view was strongly combated 

 by Heidenhain, who pointed out that many of the granules staining darkly with osmic 

 acid were not necessarily fat, and that the number of leucocytes within the villi were 

 hardly sufficient to account for the amount of material observed. According to Reuter 

 the epithelial cells take up fat in a dissolved condition through the striated border, 

 and deposit it as granules of neutral fat in the inner portion of the protoplasm. From 

 here the fat is passed on by the protoplasm by the side of the nucleus and extruded in 

 the form of very fine granules in the deeper parts of the inter-epithelial clefts, which 

 thus function as true excretory channels for the epithelial cells (Fig. 351). 



It is probable that the muscular mechanism of absorption described 

 many years ago by Briicke plays an important part in the absorption of fats, 

 but it is difficult to furnish any experimental proof of the manner in which 

 this mechanism works. Repeated contractions of the muscle fibres of the 

 villus would tend to empty the spaces into the central lacteal, and this in its 

 turn into the submucous plexus of lymphatics, so that the lymph in the 

 spaces is constantly renewed and passes laden with absorbed fat particles into 

 the valved lymphatics of the mesentery. 



